Variable intensity lamp



April 23, 1968 w. H. DORMAN VARIABLE INTENSITY LAMP Filed March 23, 1966 INVENTOR. Wllham H. Dorman MM D. 9 0% AGENT United States Patent O 3,379,869 VARIABLE INTENSITY LAMP William H. Dorman, Corning, N.Y., assignor to Corning Glass Works, Corning, N.Y., a corporation of New York Filed Mar. 23, 1966, Ser. No. 536,674 9 Claims. (Cl. 240-41.3)

ABSTRACT OF THE DISCLOSURE A lamp wherein variations in the color or intensity of the output light may be instantaneously effected by electrical means and wherein light is emitted in substantially the same pattern regardless of such variation. This is accomplished by the provision of means for producing a plurality of beams of light and a lens located to intercept such beams and having at least one surface in the form of a large number of polyhedra having faces at angles to permit the rays of the respective beams to be intercepted by one of the faces of each of the polyhedra.

This invention relates to light-projecting devices, and more particularly to a lamp having the ability to project along similar paths light beams of varying characteristics.

There often arises the need for light projectors, particularly signal lamps, wherein the color or intensity of the projected beam may easily be made to vary. One common method for effecting such variance is the mechanical interposition between the light source and the viewer of various types of filters. Another method is the selective activation of various light-producing elements within the lamp. A disadvantage of the former method is the cumbersome nature of the required apparatus and the fact that instantaneous changes cannot be effected. A disadvantage of the second method arises out of the fact that, inasmuch as the various light-producing elements must be spaced at differing locations within the lamp, the effect of the lens is to produce differing light distributions when the respective light sources are utilized.

Accordingly, it is an object of the present invention to provide a lamp wherein variations in the color or intensity of the output light may be instantaneously effected by electrical means and wherein light is emitted in substantially the same pattern regardless of such variations.

This and other objects, which will be apparent from the detailed description of the invention, are accomplished by the provision of a lamp which includes means for producing a plurality of beams of light and a lens located to intercept such beams and having at least one surface in the form of a large number of polyhedra having faces at angles to permit the rays of the respective beams to be intercepted by one of the faces of each of the polyhedra.

The invention will be described with reference to the accompanying drawing, in which:

FIGURE 1 is a front plan view of a lamp according to the invention, and

FIGURE 2 is a sectional view taken on line 22 of FIGURE 1.

Referring to the drawing, the lamp of the present invention comprises a lens 10, a reflector 12 and three independently operable light-producing elements, or bulbs, 14, 16 and 18. Reflector 12 comprises three parabolic sections 20, 22 and 24, each section extending around the rim through 120, as illustrated in FIGURE 1. Bulbs 14, 16 and 18 are located respectively at the foci of reflector sections 20, 22 and 24. The axes of the parabolic inner surfaces of the reflector sections are tilted toward longitudinal axis 26 of the lens. Thus, light emitted by each bulb and reflected by the reflector section at the focus of which the bulb is located is directed 3,379,869 Patented Apr. 23, 1968 ice against lens 10 as a beam of parallel rays impinging upon the inner surface of the lens at an angle which is the complement of the angle between the axis of the respective parabolic reflector section and the longitudinal axis of the lens.

Lens 10 comprises a multitude of small trihedral surfaces 30. The trihedra are oriented such that each trihedron has one face 32 which intercepts light which has been reflected from reflector section 20, a second face 34 which intercepts light which has been reflected by section 22 and a third face 36 which intercepts light which has been reflected by section 24. The trihedra are preferably oriented such that substantially all of the light of each collimated beam falls upon the corresponding surfaces of the trihedra. Thus, with regard to each of the three collimated beams, the effect is substantially as if there were one lens comprising all of faces 32 which acts upon the beam from reflector section 14, another lens comprising faces 34 acting upon the beam from section 16, and a third lens comprising faces 36 acting upon the beam from section 24. Each of the faces is oriented so as to refract the beam reflected by the respective reflector section such that each beam emerges from the lens in a direction parallel to axis 26 of the lens. Thus, all light falling directly upon a reflector section from the bulb associated therewith emerges from the lamp as a collimated beam parallel to the axis of the lamp. This characteristic is illustrated in FIGURE 2 with respect to the beam produced by bulb 16, wherein the arrows represent the paths of light rays reflected from reflector section 22. Therefore, when, for example, bulbs 14, 16 and 18 are of differing color, the lamp may be made to emit, by the selective individual use of the three bulbs, beams of varying color.

It will be observed that a large percentage of the light emitted by any one of the bulbs passes through the lens either after passing directly between the bulb and the lens or after being reflected by a reflector section other than that associated with the particular bulb. This light, of course, will not emerge from the lamp as a parallel beam. Such light will be emitted at varying angles, thereby permitting the lamp to be viewed from the side as Well as directly from in front of the lamp. The result is a light distribution wherein the maximum candle power of the lamp is along its axis, and lesser amounts of light are emitted at varying angles diverging therefrom.

Although varying lamp configurations may be utilized in accordance with illumination requirements, it is generally preferable, although not necessary, that the axis of each of the parabolic reflector sections form an angle between 35 and 40 with axis 26 of the lens. When such angles are utilized, and when the index of refraction of the glass comprising the lens is 1.50, the angle between the faces of the trihedra and the plane of the lens surface may vary between 55" and 61. In the illustrated embodiment, the axes of the reflector sections form angles of 35 with the axis of the lamp, and the trihedral surfaces are in the form of corners of cubes, i.e., the faces thereof form angles of with one another and angles of approximately 55 with the plane of lens 10. The lens is formed from a glass having an index of refraction of 1.50.

The described lamp has particular utility in signal systems, such as those wherein red, green, and amber signals are provided for traffic control. Such lamps may be further utilized in the tail lights of automobiles, in conjunction with means for activating the respective bulbs individually in accordance with the acceleration of the vehicle, e.g., green during positive acceleration, red during negative acceleration and amber when the vehicle is traveling at a uniform velocity. Such signals are useful to the drivers of the following vehicles.

Although for simplicity of design it is preferable that each beam which is directed toward the lens be a collimated beam, other arrangements wherein each beam is such that it falls substantially upon only one face in each polyhedron may be utilized. In such cases, the angles between the faces of the polyhedra and between the faces and the body of the lens will vary to correspond with the non-parallel relationship among the rays within each beam.

In place of bulbs of differing color, there may be substituted bulbs of differing candle power. Thus, the lamp may be caused to emit light of difiering intensities in substantially the same patterns. The bulbs may be operated either one at a time or simultaneously in various combinations to give either increased candle power or combinations of colors.

If greater spread is desired in the emitted beam, the faces of the trihedral light-reflecting elements may be provided with slight curvatures, the amount of curvature being a function of the amount of beam spread desired. Although for convenience lens 10 has been shown as being substantially planar in form, and having a flat rear surface, the entire lens may be curved, and the inner surface of the lens may be provided with further light-retracting elements.

Polyhedral light-refracting elements in forms other than trihedra may be employed to correspond with other numbers of light sources. For example, a two-way system may be produced by the use of a reflector comprising two parabolic sections each having a light source located along its axis and a lens comprising a series of dihedral prisms oriented perpendicular to the axes of the parabolas and having their respective faces located so as to intercept light collimated by the respective reflectors.

The polyhedral retracting elements employed in the lens may be formed on either surface or" the lens and may be either convex or concave polyhedra. The lens may be made in the form of a sealed beam unit, wherein the entire unit forms a single sealed bulb and bare filaments take the place of the bulbs.

Inasmuch as further modifications may be made within the scope of the invention, it is intended that the invention be limited only by the scope of the appended claims.

I claim:

1. A lamp for the projection of light of varying characteristics, said lamp comprising means for producing a plurality of beams of light and a transparent lens at a location to intercept said beams, said lens comprising a plurality of surface areas in the general form of polyhedra, each said polyhedron having a number of faces corresponding to the number of beams producible by said means, said polyhedra being oriented such that each said beam passes through each said polyhedron but substantially through a different face thereof, said faces being oriented such that each said beam emerges from said lens in substantially the same direction as a beam of substantially parallel rays.

2. A lamp according to claim 1 in which said means comprises means for producing a plurality of collimated beams at angles to one another other than parallel.

3. A lamp according to claim 1 in which said faces of said polyhedra are curved by an amount sufiicient to impart spread to said beams.

4. A lamp according to claim 1 in which said means comprises means for producing light beams of differing intensity.

5. A lamp according to claim 1 in which said means comprises a plurality of parabolic reflector sections having their axes at angles other than parallel to one another, each reflector section being provided with a light source located at its focus.

6. A lamp according to claim 1 in which said polyhedra are trihedra.

7. A lamp according to claim 6 in which said faces of said trihedra are at angles of 90 with respect to one another.

8. A lamp according to claim 1 in which said means comprises means for producing beams of diifering color.

9. A lamp according to claim 3 in which said colors are red, green and amber.

References Cited UNITED STATES PATENTS 3,222,985 12/1965 Remesat 24041.3 XR

NORTON ANSHER, Primary Examiner.

RICHARD M. SHEER, Assistant Examiner. 

